| 1. |
- Ali, Aamir, 1994, et al.
(författare)
-
Engineering Symmetry-Selective Couplings of a Superconducting Artificial Molecule to Microwave Waveguides
- 2022
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 129:12
-
Tidskriftsartikel (refereegranskat)abstract
- Tailoring the decay rate of structured quantum emitters into their environment opens new avenues for nonlinear quantum optics, collective phenomena, and quantum communications. Here, we demonstrate a novel coupling scheme between an artificial molecule comprising two identical, strongly coupled transmon qubits and two microwave waveguides. In our scheme, the coupling is engineered so that transitions between states of the same (opposite) symmetry, with respect to the permutation operator, are predominantly coupled to one (the other) waveguide. The symmetry-based coupling selectivity, as quantified by the ratio of the coupling strengths, exceeds a factor of 30 for both waveguides in our device. In addition, we implement a Raman process activated by simultaneously driving both waveguides, and show that it can be used to coherently couple states of different symmetry in the single-excitation manifold of the molecule. Using that process, we implement frequency conversion across the waveguides, mediated by the molecule, with efficiency of about 95%. Finally, we show that this coupling arrangement makes it possible to straightforwardly generate spatially separated Bell states propagating across the waveguides. We envisage further applications to quantum thermodynamics, microwave photodetection, and photon-photon gates.
|
|
| 2. |
- Besse, Jean-Claude, et al.
(författare)
-
Parity Detection of Propagating Microwave Fields
- 2020
-
Ingår i: Physical Review X. - 2160-3308. ; 10:1
-
Tidskriftsartikel (refereegranskat)abstract
- The parity of the number of elementary excitations present in a quantum system provides important insights into its physical properties. Parity measurements are used, for example, to tomographically reconstruct quantum states or to determine if the decay of an excitation has occurred, information that can be used for quantum error correction in computation or communication protocols. Here, we demonstrate a versatile parity detector for propagating microwaves, which distinguishes between radiation fields containing an even or odd number n of photons, both in a single-shot measurement and without perturbing the parity of the detected field. We showcase applications of the detector for direct Wigner tomography of propagating microwaves and heralded generation of Schrodinger cat states. This parity detection scheme is applicable over a broad frequency range and may prove useful, for example, for heralded or fault-tolerant quantum communication protocols.
|
|
| 3. |
- Eriksson, Axel, 1989, et al.
(författare)
-
Universal control of a bosonic mode via drive-activated native cubic interactions
- 2024
-
Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
-
Tidskriftsartikel (refereegranskat)abstract
- Linear bosonic modes offer a hardware-efficient alternative for quantum information processing but require access to some nonlinearity for universal control. The lack of nonlinearity in photonics has led to encoded measurement-based quantum computing, which relies on linear operations but requires access to resourceful (’nonlinear’) quantum states, such as cubic phase states. In contrast, superconducting microwave circuits offer engineerable nonlinearities but suffer from static Kerr nonlinearity. Here, we demonstrate universal control of a bosonic mode composed of a superconducting nonlinear asymmetric inductive element (SNAIL) resonator, enabled by native nonlinearities in the SNAIL element. We suppress static nonlinearities by operating the SNAIL in the vicinity of its Kerr-free point and dynamically activate nonlinearities up to third order by fast flux pulses. We experimentally realize a universal set of generalized squeezing operations, as well as the cubic phase gate, and exploit them to deterministically prepare a cubic phase state in 60 ns. Our results initiate the experimental field of polynomial quantum computing, in the continuous-variables notion originally introduced by Lloyd and Braunstein.
|
|
| 4. |
- Gasparinetti, Simone, 1985
(författare)
-
Photons go one way or another
- 2023
-
Ingår i: Nature Physics. - : Springer Science and Business Media LLC. - 1745-2481 .- 1745-2473. ; 19:3, s. 310-311
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
|
|
| 5. |
- Hillmann, Timo, 1995, et al.
(författare)
-
Universal Gate Set for Continuous-Variable Quantum Computation with Microwave Circuits
- 2020
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 125:16
-
Tidskriftsartikel (refereegranskat)abstract
- We provide an explicit construction of a universal gate set for continuous-variable quantum computation with microwave circuits. Such a universal set has been first proposed in quantum-optical setups, but its experimental implementation has remained elusive in that domain due to the difficulties in engineering strong nonlinearities. Here, we show that a realistic three-wave mixing microwave architecture based on the superconducting nonlinear asymmetric inductive element [Frattini et al. , Appl. Phys. Lett. 110 , 222603 (2017)] allows us to overcome this difficulty. As an application, we show that this architecture allows for the generation of a cubic phase state with an experimentally feasible procedure. This work highlights a practical advantage of microwave circuits with respect to optical systems for the purpose of engineering non-Gaussian states and opens the quest for continuous-variable algorithms based on few repetitions of elementary gates from the continuous-variable universal set
|
|
| 6. |
- Kudra, Marina, 1992, et al.
(författare)
-
High quality three-dimensional aluminum microwave cavities
- 2020
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:7
-
Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive study of internal quality factors in superconducting stub-geometry three-dimensional cavities made of aluminum. We use wet etching, annealing, and electrochemical polishing to improve the as machined quality factor. We find that the dominant loss channel is split between the two-level system loss and an unknown source with a 40:60 proportion. A total of 17 cavities of different purity, resonance frequency, and size were studied. Our treatment results in reproducible cavities, with 10 of them showing internal quality factors above 80 x 10(6) at a power corresponding to an average of a single photon in the cavity. The best cavity has an internal quality factor of 115 x 10(6) at a single photon level. (C) 2020 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http:// creativecommons.org/licenses/by/4.0/).
|
|
| 7. |
- Kudra, Marina, 1992, et al.
(författare)
-
Robust Preparation of Wigner-Negative States with Optimized SNAP-Displacement Sequences
- 2022
-
Ingår i: PRX Quantum. - : AMER PHYSICAL SOC. - 2691-3399. ; 3:3
-
Tidskriftsartikel (refereegranskat)abstract
- Hosting nonclassical states of light in three-dimensional microwave cavities has emerged as a promising paradigm for continuous-variable quantum information processing. Here we experimentally demonstrate high-fidelity generation of a range of Wigner-negative states useful for quantum computation, such as Schrodinger-cat states, binomial states, Gottesman-Kitaev-Preskill states, as well as cubic phase states. The latter states have been long sought after in quantum optics and have never been achieved experimentally before. We use a sequence of interleaved selective number-dependent arbitrary phase (SNAP) gates and displacements. We optimize the state preparation in two steps. First we use a gradient-descent algorithm to optimize the parameters of the SNAP and displacement gates. Then we optimize the envelope of the pulses implementing the SNAP gates. Our results show that this way of creating highly nonclassical states in a harmonic oscillator is robust to fluctuations of the system parameters such as the qubit frequency and the dispersive shift.
|
|
| 8. |
- Lu, Yong, 1989, et al.
(författare)
-
Characterizing decoherence rates of a superconducting qubit by direct microwave scattering
- 2021
-
Ingår i: npj Quantum Information. - : Springer Science and Business Media LLC. - 2056-6387. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally investigate a superconducting qubit coupled to the end of an open transmission line, in a regime where the qubit decay rates to the transmission line and to its own environment are comparable. We perform measurements of coherent and incoherent scattering, on- and off-resonant fluorescence, and time-resolved dynamics to determine the decay and decoherence rates of the qubit. In particular, these measurements let us discriminate between non-radiative decay and pure dephasing. We combine and contrast results across all methods and find consistent values for the extracted rates. The results show that the pure dephasing rate is one order of magnitude smaller than the non-radiative decay rate for our qubit. Our results indicate a pathway to benchmark decoherence rates of superconducting qubits in a resonator-free setting.
|
|
| 9. |
- Lu, Yong, 1989, et al.
(författare)
-
Propagating Wigner-Negative States Generated from the Steady-State Emission of a Superconducting Qubit
- 2021
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 126:25
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally demonstrate the steady-state generation of propagating Wigner-negative states from a continuously driven superconducting qubit. We reconstruct the Wigner function of the radiation emitted into propagating modes defined by their temporal envelopes, using digital filtering. For an optimized temporal filter, we observe a large Wigner logarithmic negativity, in excess of 0.08, in agreement with theory. The fidelity between the theoretical predictions and the states generated experimentally is up to 99%, reaching state-of-the-art realizations in the microwave frequency domain. Our results provide a new way to generate and control nonclassical states, and may enable promising applications such as quantum networks and quantum computation based on waveguide quantum electrodynamics.
|
|
| 10. |
- Lu, Yong, 1989, et al.
(författare)
-
Steady-State Heat Transport and Work With a Single Artificial Atom Coupled to a Waveguide: Emission Without External Driving
- 2022
-
Ingår i: PRX Quantum. - 2691-3399. ; 3:2
-
Tidskriftsartikel (refereegranskat)abstract
- We observe the continuous emission of photons into a waveguide from a superconducting qubit without the application of an external drive. To explain this counterintuitive observation, we build a two-bath model where the qubit couples simultaneously to a cold bath (the waveguide) and a hot bath (a secondary environment). Our results show that the thermal-photon occupation of the hot bath is up to 0.14 photons, 35 times larger than the cold waveguide, leading to nonequilibrium heat transport with a power of up to 132 zW, as estimated from the qubit emission spectrum. By adding more isolation between the sample output and the first cold amplifier in the output line, the heat transport is strongly suppressed. Our interpretation is that the hot bath may arise from active two-level systems being excited by noise from the output line, and that the qubit coherence can be improved significantly by suppressing this noise. We also apply a coherent drive, and use the waveguide to measure thermodynamic work and heat, suggesting waveguide spectroscopy is a useful means to study quantum heat engines and refrigerators. Finally, based on the theoretical model, we propose how a similar setup can be used as a noise spectrometer which provides a solution for calibrating the background noise of hybrid quantum systems.
|
|
